First, download Jing, a product from the same people who made Snagit (Techsmith).
Install Jing. You will notice a yellow sun at the top center, or top right corner of your screen.
Hover over it and click the + sign. Now you will highlight the area you wish to record. Click and drag a rectangle over a large section of your screen (where the action is). Then click the 'film strip' button. You will now start recording!
When you're done, hit the Stop button (the square). Next, click the "Upload to Screencast" button (it's the first selection on the left). Jing will upload the video and automatically copy a link to your clipboard.
Copy that link into your forum post! Forum users now can see exactly what you see and makes for a much better troubleshooting experience.